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Most of the aluminum intakes, are pretty similar. Personally, I think the 69 Z/28 302 intake (3932472), and the 70 3972110 LT-1 intake, were probably about the best. The 71-72 LT-1 intake is pretty good too. These were the last of the production performance intakes, and as such, benefited from the most development.
Most of the aluminum intakes, are pretty similar. Personally, I think the 69 Z/28 302 intake (3932472), and the 70 3972110 LT-1 intake, were probably about the best. The 71-72 LT-1 intake is pretty good too. These were the last of the production performance intakes, and as such, benefited from the most development.
Did you use intake gaskets that blocked off the exhaust gas port cross-over channel? I see that you installed a heat shield under the carb which is why I ask?
Also, I noticed the ball valve installed on the coolant hose. Have you found that an effective means to reduce cabin heat, and during a long drive does heat migration through the return hose become an issue? I'm thinking of installing a similar valve, and followed the forum debate, if you will, of installing a valve on both hoses.
Did you use intake gaskets that blocked off the exhaust gas port cross-over channel? I see that you installed a heat shield under the carb which is why I ask?
Also, I noticed the ball valve installed on the coolant hose. Have you found that an effective means to reduce cabin heat, and during a long drive does heat migration through the return hose become an issue? I'm thinking of installing a similar valve, and followed the forum debate, if you will, of installing a valve on both hoses.
Speaking for myself, it made a HUGE difference! Only need one valve.
KSL'67 I can tell you on a otherwise stock 327 365 hp non air car I tried the heat crossover passage block offs and the car ran like crap and had a weird fluttering sound almost like two 4 cylinder engines not one V8, with them blocked off there wasn't enough heat to vaporize the raw fuel, and it may also be something to do with the 365 hp intake manifold design so at least check into it a little more before you do this.
KSL'67 I can tell you on a otherwise stock 327 365 hp non air car I tried the heat crossover passage block offs and the car ran like crap and had a weird fluttering sound almost like two 4 cylinder engines not one V8, with them blocked off there wasn't enough heat to vaporize the raw fuel, and it may also be something to do with the 365 hp intake manifold design so at least check into it a little more before you do this.
JRRHINO - I blocked off the intake heat cross-over passage a year ago with intake gaskets that have the blocking plate as well as added a 1/2" phenolic spacer between the carb and the intake manifold. In the process of curing my fuel percolation and hot starting issues blocking off the crossover port produces a tinny exhaust note at idle rather than the deep throated bass car guys love. While driving, backing off the gas while on throttle just doesn't produce the pleasing side pipe exhaust notes that I enjoyed.
On a positive note, my heat gun readings are proof positive that the blocked port has cooled the manifold over 100 degrees to under 200 degrees. In hot California that is significant. I have no cold starting or warm-up issues either.
So for now, I'll keep convincing myself that the cure is better than the heat related problems.
JRRHINO - I blocked off the intake heat cross-over passage a year ago with intake gaskets that have the blocking plate as well as added a 1/2" phenolic spacer between the carb and the intake manifold. In the process of curing my fuel percolation and hot starting issues blocking off the crossover port produces a tinny exhaust note at idle rather than the deep throated bass car guys love. While driving, backing off the gas while on throttle just doesn't produce the pleasing side pipe exhaust notes that I enjoyed.
On a positive note, my heat gun readings are proof positive that the blocked port has cooled the manifold over 100 degrees to under 200 degrees. In hot California that is significant. I have no cold starting or warm-up issues either.
So for now, I'll keep convincing myself that the cure is better than the heat related problems.
First, I'm in 100% agreement that the 67-72 Z28/LT1 intakes are the overall best. The 67-72 manifolds are basically the same, but there are a few minor variations in them. First, the 67-68 version is the most noticeably different from the 69-72 version. The major difference is at the front of the manifold in several of the water passage areas.
Below is a comparison between the 67-8 and 69-72 versions. The one on the left is the 67-8 version. Notice the position of the opening for the thermostat/housing. Also, the threaded holes for a heater hose fitting are in different locations. Actually, on the left one, that hole is for the temp sender on 67 models. The temp sender moved to the left head for 68.
The left (67-8) version has a threaded hole for the alternator adjusting bracket (and air cond brace if applicable). The right one does not.
This manifold is installed on a 68 Chevelle (my son's). Unfortunately the attachment bolt for the alt bracket (and air cond brace) is covered by the upper radiator hose.
Up through 68 on pass cars, such as Camaros, the alternator was ALWAYS mounted on the left side. Then in 69 (on pass cars), the alt was moved over to the right side, thus the threaded bolt hold up front was no longer needed and there was a need to reposition the outlet for the thermostat. This style manifold WAS NOT used on Vettes until the introduction of the 70 LT1.
All 67-69 versions had the hole up front for an oil fill tube (WHICH I PREFER!), but the 69 versions had a plug installed in the oil fill tube hole. The boss for an oil fill tube was still on the 70-72 manifolds, but it was cast closed. Some 70-72 versions that I've seen had a VERY shallow depression where the hold would be for an oil fill tube.
Of course, it will never be seen, but there are also some minor variations on the under side of the 67-8 and 69-70 versions.
As far as blocking off the exhaust cross over passage under the carb, that's a personal choice depending on your climate area. I have a 68 Z28 manifold on a SB400 in the Chevelle and I blocked off the passage. In cold weather or for the first startup for the day (I'm in Okla), the engine has to build up some heat before it will not hesitate from a stop. But once the engine is hot, there is no hesitation. I can't adjust the choke to stay closed longer because there is very little heat transferred to the pocket for the choke pulloff spring.
This is the 69 style manifold on the SB400 in our 70 Chevelle (can't see much of it!!!). Notice the routing of the upper radiator hose compared to the 68 above.
For a car that is a driver, I MUCH PREFER a Q-jet over a Holley. This requires using a Mr. Gasket adapter plate between the manifold and the carb.
KSL'67 I can tell you on a otherwise stock 327 365 hp non air car I tried the heat crossover passage block offs and the car ran like crap and had a weird fluttering sound almost like two 4 cylinder engines not one V8, with them blocked off there wasn't enough heat to vaporize the raw fuel, and it may also be something to do with the 365 hp intake manifold design so at least check into it a little more before you do this.
I blocked off my exhaust crossover and I'm very pleased with the results. I did notice that it takes a few minutes longer to warm up, but living in South Florida, that really isn't an issue. You are correct about the slight drop-off in fuel being vaporized. To counter this, at the advice of a friend of mine who has been a mechanic and engine builder for 30 years, he told me to go from a 65 primary jet to a 68 on my 2818 Holley. The funky exhaust note was easily fixed with a "H" pipe. A muffler shop charged about 100 bucks to make one up, and install. My car has never sounded, or run better.
I blocked off my exhaust crossover and I'm very pleased with the results. I did notice that it takes a few minutes longer to warm up, but living in South Florida, that really isn't an issue. You are correct about the slight drop-off in fuel being vaporized. To counter this, at the advice of a friend of mine who has been a mechanic and engine builder for 30 years, he told me to go from a 65 primary jet to a 68 on my 2818 Holley. The funky exhaust note was easily fixed with a "H" pipe. A muffler shop charged about 100 bucks to make one up, and install. My car has never sounded, or run better.
I have NEVER liked the toned down sound of a car that has an H or X pipe. After 62, they were no longer installed on Corvettes and never installed on passenger cars (full size, Novas, Camaros, Chevelles, etc).
I like a car best with headers and true dual exhaust with NO crossover.
First, I'm in 100% agreement that the 67-72 Z28/LT1 intakes are the overall best. The 67-72 manifolds are basically the same, but there are a few minor variations in them. First, the 67-68 version is the most noticeably different from the 69-72 version. The major difference is at the front of the manifold in several of the water passage areas.
Below is a comparison between the 67-8 and 69-72 versions. The one on the left is the 67-8 version. Notice the position of the opening for the thermostat/housing. Also, the threaded holes for a heater hose fitting are in different locations. Actually, on the left one, that hole is for the temp sender on 67 models. The temp sender moved to the left head for 68.
The left (67-8) version has a threaded hole for the alternator adjusting bracket (and air cond brace if applicable). The right one does not.
This manifold is installed on a 68 Chevelle (my son's). Unfortunately the attachment bolt for the alt bracket (and air cond brace) is covered by the upper radiator hose.
Up through 68 on pass cars, such as Camaros, the alternator was ALWAYS mounted on the left side. Then in 69 (on pass cars), the alt was moved over to the right side, thus the threaded bolt hold up front was no longer needed and there was a need to reposition the outlet for the thermostat. This style manifold WAS NOT used on Vettes until the introduction of the 70 LT1.
All 67-69 versions had the hole up front for an oil fill tube (WHICH I PREFER!), but the 69 versions had a plug installed in the oil fill tube hole. The boss for an oil fill tube was still on the 70-72 manifolds, but it was cast closed. Some 70-72 versions that I've seen had a VERY shallow depression where the hold would be for an oil fill tube.
Of course, it will never be seen, but there are also some minor variations on the under side of the 67-8 and 69-70 versions.
As far as blocking off the exhaust cross over passage under the carb, that's a personal choice depending on your climate area. I have a 68 Z28 manifold on a SB400 in the Chevelle and I blocked off the passage. In cold weather or for the first startup for the day (I'm in Okla), the engine has to build up some heat before it will not hesitate from a stop. But once the engine is hot, there is no hesitation. I can't adjust the choke to stay closed longer because there is very little heat transferred to the pocket for the choke pulloff spring.
This is the 69 style manifold on the SB400 in our 70 Chevelle (can't see much of it!!!). Notice the routing of the upper radiator hose compared to the 68 above.
For a car that is a driver, I MUCH PREFER a Q-jet over a Holley. This requires using a Mr. Gasket adapter plate between the manifold and the carb.
Good stuff!! Thanks for posting. Been a long time since we used to be able to spot those intakes for cheap at the swap meet and I had to notice which version it was. Thanks for the refresher!
Did you use intake gaskets that blocked off the exhaust gas port cross-over channel? I see that you installed a heat shield under the carb which is why I ask?
Also, I noticed the ball valve installed on the coolant hose. Have you found that an effective means to reduce cabin heat, and during a long drive does heat migration through the return hose become an issue? I'm thinking of installing a similar valve, and followed the forum debate, if you will, of installing a valve on both hoses.
Absolutely made a difference having the ball valve shut off hot coolant to the inside of the car. You only need the 1 valve. If it's shut off, it's shut off. Yes my exhaust gas port cross-over channel was blocked off using, I think, some sort of epoxy material. No issues. Even though I am an a cold climate area, I have my choke shut off as well so the primary butterfly is always wide open. I just feather the gas for the first mile and I'm good to go.
Here's a couple of pics of the impact that aluminum heat shield under the carb has on the temps of the primary bowl. This WORKS!
Absolutely made a difference having the ball valve shut off hot coolant to the inside of the car. You only need the 1 valve. If it's shut off, it's shut off. Yes my exhaust gas port cross-over channel was blocked off using, I think, some sort of epoxy material. No issues. Even though I am an a cold climate area, I have my choke shut off as well so the primary butterfly is always wide open. I just feather the gas for the first mile and I'm good to go.
Here's a couple of pics of the impact that aluminum heat shield under the carb has on the temps of the primary bowl. This WORKS!
Jim
In God We Trust!
Temp on thermostat housing
Temp on primary fuel bowl
Thanks for the readings. I'm going to add the ball valve; it's too easy a mod to make and remove.
Now, what performance benefit can be expected from a new intake manifold, and what manufacturer is recommended?
03-13-2015, 05:59 PM
I'm partial to the 69 Z/28 manifold myself. 
